Ceramic insulating materials are well known for protecting alloy and composite substrate materials from high temperature environments. Incorporated by reference herein are U.S. Pat. Nos. 6,013,592 and 6,197,424 that describe high temperature insulations for ceramic matrix composite materials. Further protection against a high temperature water vapor environment may be provided by a protective coating applied over the insulating material, as described in U.S. patent application publication 2003/0035907, also incorporated by reference herein.